Electrical transfer network



April 1950 L. J. GIACOLETTO 2,504,322

ELECTRICAL TRANSFER NETWCRK Filed June 10, 1949 DWI/00E m; 74 65 INVENTOR ATTORNEY Patented Apr. 18, 1950 UNI STATES PATEN O F F 1 CE 7 ELECTRICAL TRANSFER NETWORK Lawrence J Giao oletto, Eatontown, N. J assignor to Radio Corporation of. America,".azcorporation of Delaware 'Applica'tionx..lune; 10, 1949, Serial No. 98,302

1 16 "Claims. (01. 315-.-2D1) :An. electrical.transferlnetwork, as that term -is usedhereinand initheappended claims, is intended. to referitoa n'etwork'in which an electron. stream. is used. to. complete circuit connectionsLbetweenfidifierent, points. In many instances, oneiorl both of the points to be connected in a givenlcircu'itare at alhigh potential solthat .difliculties. are. encountered with respe'ct'jtoithe ieffec'tivexinsulation .of elements "operating at widely differing: potentials.

The invention is applicable .to half wave and full -wave rectifiers, "voltage-doubling-rectifying "circuits,"a1id,"in general,"tocircuits involving a "switching action. For example, an electric sv'vitchingcircuit maybe required to'co'nnecta source terminal to' a -load-terminal only when the potential of the-source terminal exceedsa predetermined value as it varies between values J above and below the potential-ofthe load terminal. Byway of further exampla'butnotilimitzation; the invention .iS applicable 1' to rectifying networks for converting energy from a'source of varying potential into a steady 1 direct potential for such use as may bedesired.

In this connection. it" :may he observed that the potential variationmay be referredto ground potential, in which case-"it lSQOi'lVBllblOll'ZillY considered too-be falternating,:orto-any other .cir-

cuit pointrwhich. may orlmay not be at ground potential. .Asliere considered, an alternating potential is one which. varies in. amplitude-with respect to any pointer reference.

A specific. typefi'oi Icircuit .tolwhich. the. invention is, particularly applicable is a capacitor 'chargingand/or discharging circuit. .Heretofore,

it has been customary to charge a capacitor from.

an alternating potentialisource by means of a suitable rectifier; such as an electron discharge device 'ofthethermionic 'dio'de' type having an 'electron-emissive' cathode heated by" heat conduction and/or radiation'from a separate heater filament. When operating at relatively" high positive potentials; for example, when the circuit -is being employed 'as" a voltage 'doubling' circuit, or as a circuit for-developing accelerating potentials for kinesc'ope' tubes, the cathode of i the .thermimic :"diode "normally operated' at the positive direct current potential oi'i'the supply circuit abovaground, and. atthe; same time the fi'filament' or: .h'eatertzis connected to" a? source of F heating. potential. This-:m'eansifth'ati. either the heater supply circuit also-must be operated'at the high direct current otential of the cathode, or,

if the heater is operated at or near ground potential, the heater must be insulated from the oathode towithstand the full direct cur-rent output voltage.

The first expedient involves insulating the secondary Winding of -.the filament heating transformer fromthe primary Winding, or the useof separate batteries floating-at the high potential aboveground. On theother hand, when the heater is. operatedator near ground potential, the insulation between heaterand cathode, if suflicientto Withstandithe high .potential difierence .between .those electrodes. reduces. the

Lheat transfer; efficiency.

Itis a general object oiirnyinvention to provide an electrical transfer. networkin which. a

high voltageypo'sitive terminalof a load maybe lated from circuit.elementsoperating. at ground .potentialsthan has heretofore beenipossible.

,A more specificobiect of my invention is to providean ,electricaltransfernetwork in which a highvoltage positive load. terminal. is con- -nected to anelectron .ldischarge electrode which rendered .eiectroneemissive byubombardment with i elemental energy articles, from. .a source which is spatiallyremoved iromeaid electrode. .Accordingto one modification of" my. invention,. the electron discharge. electrodeis bombardedby primary. electrons. from a thermionic cathode.

. According. to-another modification of. the, invention, the electron discharge electrode is bombarded by. photons from a source relatively spatially removedrfrom the electrode.

Otheraspects of my invention relates to circuit arrangements in which the full advantages of my invention are. attained.

Howzthe foregoing. and other objects are attained will appear more. fully from. the description which follows hereinbelow .andthe drawings, in which:

Figure 1 illustrates changes in dynode current with changes in dynode potential in a secondary electron emission devices;

Figure 2 illustrates a'basic rectifying circuit employing a secondary emission discharge vice as a unidirectional valve in accordance with the invention;

Figures 3 and 4 are modifications of the ciredit of Figure 2 'Figure' fi 'illustrates theapplication of my intery Be, With polarity as indicated.

vention to voltage multiplier circuits, with rectification and switching being accomplished by means of secondary emission;

Figure 6 illustrates the application of the invention to a voltage multiplication circuit in which rectification and switching are accomplished by means of photo-emission; and

Figure '7 illustrates a circuit in which a current of varying potential is derived from a condenser whose capacity is periodically varied between maximum and minimum values by a me chanical drive arrangement and in which the condenser is charged and discharged by means of secondary electron discharge devices.

Similar reference numerals identify similar parts throughout the several figures of the drawings.

In conventional high voltage circuits of the type mentioned above, employing conventional diodes embodying thermionic cathodes, the cathode must be directly or indirectly heated from a low voltage source and in the latter case the cathode may either be insulated from the source or operated at the source potential.

In the various arrangements illustrated herein, the electrode which functions as the cathode electrode is energized by bombardment by elemental energy particles, such as electrons or photons derived from a source which is disposed at some distance from the emitting electrode. Consequently, the device may take the form of a known type of secondary-electron discharge tube, in which case the electrode which functions as a source of electrons is called a dynode.

If a secondary-electron emitting electrode or dynode having good secondary-electron emission properties is bombarded with electrons of sufiicient energy to release secondary electrons from the dynode surface, and if a second electrode maintained at fixed positive potential be provided to collect secondary-electrons emitted by the dynode, then the dynode current as a function of dynode potential is as shown in Figure 1. It will be seen that for a range of dynode voltage from slightly above zero to approximately the potential of the collector electrode, the dynode current is negative. For this range of dynode voltage, the dynode emits a larger number of secondaryelectrons than the number of primary-electrons striking it, and can, therefore be considered as a cathode, and the dynode-collector operation is somewhat analogous to the cathode-anode operation of a conventional thermionic diode.

An arrangement employing a secondary-electron emission device as a rectifier is illustrated in Figure 2. The tube 1 is provided with a thermionic cathode B heated in the normal manner by a heater s, which is energized by a source of low-voltage alternating current (not shown). High voltage alternating current from the secondary winding of a transformer i5 is applied to to a collector electrode H, and to a dynode iii in series with a capacitor E2. The collector l l is connected to the cathode 8 through a small bat- When the potential or" the dynode it of Figure 2 swings to a value below that of the collector H (but still a positive with respect to the cathode 8), secondnesium characterized by having a large ratio S e of secondary-electrons to primary-electrons striking the dynode, and the dynode current will be (S1) times as large as the primary or cathode current.

During the period when the dynode It is positive with respect to the collector I! there will be no secondary-emission, and the primary or cathode current flow will tend to discharge the condenser 12. However, if S is much greater than 1, this discharge current will be small as compared with the charging current, and each successive cycle will increase the charge on the capacitornlz. Rectified output voltage may be derived from output terminals T and filtered as desired. I

According to the invention, I may substantially eliminate the small discharge current previously mentioned by connecting the collector electrode to a point of alternating currrent potential which is out of phase with the dynode and cathode potentials. For example, in the circuit shown in Figure 3, the dynode it and the collector H in the tube 1 are connected to the opposite ends l3, ill of the split secondary winding of a power transformer !5'. An alternative placement of the capacitor i2 is also shown in Figure 3, wherein the capacitor i2 is connected in series between the two sections of the secondary winding of the transformer 15. This arrangement places the positive D. C. output terminal at A. C. ground potential.

In the circuit of Fig. 3, when the dynode ii! is positive with respect to the cathode 8, the collector El will be negative with respect to the cathode. Due to the relatively close spacing between the cathode 8 and the collector ii, the latter will exert an electrostatic influence on the surface of the cathode similar to the effect of a current-control grid, and will substantially eliminate the flow of primary electrons from the cathode to the dynode. Such a connection also makes the battery E0 of Fig. 2 unnecessary, since the collector M will be slightly positive with respect to the cathode 8 when the dynode it is negative.

According to another aspect of the invention, the primary current from the cathode i to the dynode ill can be substantially eliminated during the period when the dynode is positive with respect to the collector electrode by adding a control grid is to the tube 1, as shown in Fig. 4. In the circuit of Fig. l, the control grid is is energized with a voltage which is 180 out of phase with the dynode potential. For example, the control grid 15 can be connected to a point is, on the split secondary winding of the transformer H5, at which point the voltage will be 180 out of phase with the voltage on the dynode It. A self-biasing network, consisting of a capacitor l3 and a resistor I9, can be connected in the grid circuit, as shown. The collector electrode ll should he maintained at a positive potential with respect to ground, either by connecting the collector i i to a direct current source E0 as illustrated in Fig. 2, or to a properly phased alternating current source as illustrated in Fig. 3. In either the circuit of Fig. 3 or that of Fig. i, cathode current will flow only during the pe riod when the dynode potential has its smallest positive value.

In the circuit of Fig. 4, the operating angle of the cathode current (i. e. the portion of the cycle during which the capacitor l2 will be discharged accessegrid leak,- serving to-maintain the grid I 6 at or below the level .of cut-off :except during the period when the'dynode potential is atits smallest value.

If the operating angle 'of the cathodecurrent extremely small, difficulty may be experienced in getting'theroutput voltage to buildup across-the condenser I2; This isb'ecauserthedynode II will be negative with respect 'tothe cathode 8, so that the primary electrons may notxstrike the 'dynode.

This condition can be-avoided by increasing the.

operating angle of the cathode current, either by decreasing the effective collector bias. with respect to the 'ca'thode voltage, or by increasing the alternating potential on the dynode gradually as the output voltage builds up, or, alternatively; :by primingthe condenser-|2 witha- D. C. voltage.

It should be noted that, since the dynode current will be negative, the resulting load across'the secondary winding of the transformer i 5' will also hep negative; that is, the D. C. output power will be obtaine'd directly-from the potential source'for the collector electrode, and the flow of dynode current will tend to unload the secondary winding, increasing the efficiency of the driving source. For the same reason, voltage regulation of the direct-current-output will be improved, and will be much superior to conventional diode rectifier circuits.

According to another aspect of the invention, I may employ secondary electron emission tubes in a' full-wa've multiplier arrangement, as-illustrated in Fig. 5. Inthis case, I employ a, pluralityof condensers 2!], 2 I, 22 :and 23, and an equal number of secondary emission discharge tubes 24, 25, 2'5 and 21. In the circuit of Fig. 5, the dynodes ill in. the first and third tubes 24, 26 are both-connected to one end I! of thesecondary winding of the transformer l 5 through the first'and third capacitors 2o, 22, while the collector electrodes ll in thesame tubes 24, 26 are connected to the other (grounded) end I? of the transformer secondary winding, so that the firstand third tubes 24., 25 will operate in the manner already described hereinabove. The dynodes l and the collector electrodes I! in the :second and fourth tubes 25, 21 are connected to the secondary winding of the transformer iii in inverse relation with respect to the dynodcs I ll and the collectors l I in the first and third tubes 24, 26, so that the second and fourth tubes 25, 2'! will operate in the same manner as do the first and third tubes 24, 2B, but on opposite half-cycles of transformer voltage. While I have not illustrated in Fig.

? any arrangement for preventing discharge of the condensers -23 by the primary cathode current during the time interval when the respective dynodes swing above the collector potential, it will be understood that the arrangements illustrated in Figs. 3'or 4 may be employed. Those skilled in the art will also understand that the'control potentials applied to the collectors I! '(or tocontrol grids thereof, if such are used) of the secondandfourth tubes and "2'! must be phased 180. from the control potentials applied to the corresponding electrodes of the first and third tubesZ I and 26;

The output voltage obtainable at'the dynode ill ofthe fourth tube 21 will be approximately four times the voltage obtainable with a single stage, other "circuit parameters being equal.

It should be noted that, since the cathodes 8 0i all of the tubes 24-21. in the network ofFig.

iii)

6 51am: operated/at the samepotential, a oneenvelope tube-employing a common cathode may. replace. the individual tubes 24-21 shown in Fig. 5.

Turningnow to the use of photo-emissive electrodes for. transferring charges at high vpotentials, attention is directed to Fig. 6, in which I have illustrated a photo-electric electron discharge device in-a voltage multiplier circuit similar to that shown in Fig. 5. The arrangement of Fig. 6 comprises three torroidal evacuated envelopes 2'8, 29, 30, containing, respectively, cylindrical photo-emissive electrodes 3|, 32, 33, and collector electrodes 34, 35 and 36. Within the cylindrical space defined by the envelopes 28, 29, is a light source, such as an incandescent lamp 31, preferably disposed along the axis of the envelopes, and having a filament 38 adapted to be heated to incandescence by the passage therethrough of an electric current from a suitable source (not shown).

The phcto-emissive electrodes 3!, 33 in the firstan'd third tubes 28, 3!! are connected to one terminal I! of the secondary winding of a transformer l5 through capacitors 20, 22, while the collector electrodes 34, 36 in the first and third tubes-28, 30' are connected to the other terminal H of the transformer secondary, with a third capacitor 2| being connected between the two collectors 34, 36. The photo-emitter 32 and the collector in the second tube 29 are connected to the transformer secondary inversely with respect to the connections for the first and third tubes 28, 30.

In this arrangement, photons emitted by the filament 38 will pass through the screen-like oollectcr electrodes 34, 35, 36, and will strike the inner Surfaces of the photo-emissive electrodes SI, 32, 33 with suificient energy to dislodge electrons. When any one of the collector electrodes 34-36 is momentarily at a positive potential with respect to its associated photo-emissive electrode, a current will flow, charging the condenser in the circuit of the photo-emissive electrode, thus affording a mode of operation similar to that illustrated in Fig. 5. A D. C. voltage, having a value equal approximately to three times the peak A. C. Voltage across the transformer secondary winding,.willbe available at the output terminals T.

As is well understood in the art, the output potential obtainable from voltage multiplier circuits of the type illustrated in Figs. 5 and 6 de pends-upon the value of the alternating potential across the secondary winding of the transformer i5 and the number of condensers and rectifier elements in the circuit. Heretoiore, the output voltage obtainable in a circuit of this type was limited by the high voltage insulation problem towhich reference has already been made. In both of the circuits of Figs. 5 and 6, the high voltage insulation problem is eliminated, so that the only-limitation on the output voltage which can be obtained by increasing the number of con- 'densers and'rectifiers is the breakdown potential betweenthe various parts of the apparatus.

It shouldalso be understood that the invention is not-limited to circuits in which the alternating potential is obtained from a transformer or other electromagnetic device. In Fig. 7, I have illustrated how the invention may also be used torectify the pulsating high voltage output from an electrostatic generator of high potentials of the type illustrated and claimed in my copendin g application Serial No. 98,303, filed June 10, 1945..

iable condenser comprising a grounded plate 39,.

a dielectric layer 40, an ungrounded plate 4|, an electromagnetic driving mechanism 42 for increasing and decreasing the spacing between the plates 39, 4|, and a source of electrical energy, such as an alternating current generator 43, for energizing the driving mechanism 42. The operation of electrostatic generators of this type depends upon the fundamental fact that a condenser which is charged from a source of given potential while the condenser is adjusted to maximum capacity can be discharged at a much higher potenial after the capacity has been reduced, as by increasing the spacing between the plates, or by decreasing the confronting area of the plates, or both.

In this type of electrostatic generator, it is desirable to disconnect the charging source at a moment no later than the moment at which the capacity begins to decrease, and it is also desir- 1 able to eliminate the necesstiy of making and breaking contacts in an ionizable medium at the necessarily high potentials involved, to prevent arcing and related problems.

In the arrangement of Fig. 7, I accomplish the switching necessary for both the charging and discharging operations by means of secondary-electron emission devices. In Fig. 7 I have illustrated a switching tube 45 containingathermionic cathode 46 operated slightly below ground potential, a dynode electrode 41 connected to the ungrounded condenser plate 4|, and a collector electrode 48 connected to the positive terminal of a source of charging potential 59, the other terminal of which is grounded. When primary electrons from the cathode '46 strike the dynode 47, secondary electrons will be emitted by the dynode 47 and will be collected by the collector 48, so that the potential of the condenser plate 4| will be raised substantially to the potential of the positive terminal of the source 59. If the plate 4| is charged while in the position indi-- cated by the solid outline, and then shifted to the position indicated by the dotted outline, the potential of the capacitor will rise above the potential of the collector 48, and secondary electrons will no longer flow to the collector.

At the same time, primary electrons from the cathode 45 will also be striking a second dynode 49 which is connected to an output condenser 50. The condenser plate 4| is also connected to a second collector electrode 5|. As the condenser plate 4| moves away from the plate 39, the potential on the collector 5| will increase to a value above the potential on the dynode 49, and electrons will be drawn from the output circuit, increasing the potential across the condenser 59.

When the condenser plate 4| starts back toward the plate 39, the potential on the collector 5| will fall below the potential on the dynode 49, and the right-hand section of the tube will become inoperative. Until the dynode 4'? falls below the potential of the collector 48, no change in the charge on the plate 4| will occur. How.- ever, before the plate 4! reaches the position indicated by the solid outline, the potential thereon will fall to the potential of the collector 48, whereupon electrons will be moved from the plate 4|, and thecondenser (39, 4|) will resume the condition of maximum capacity and, once again, will be charged to the potential of the source 59.

Actually, of course, the primary electrons from the cathode 46 will tend to reduce the charge on the condenser plate 4| when the potential on the latter is more positive than that of the collector 48, and primary electrons will also tend to reduce the charge on the output condenser 50 during the period when the potential on the plate 4| is below the potential of the condenser 50. These losses in charge may be prevented by providing each half of the tube 45 with a grid 52, 53, which may be energized 180 out of phase with one another by voltage from a transformer 54 whose operation is synchronized with the operation of the mechanical drive 42, as by providing a connection from the generator 43 to the primary winding of the transformer 54. A bias battery 55 may be provided to insure cut-01f during the critical period.

Each of the arrangements hereinabove described and illustrated is characterized by the fact that energy is transferred through an elec-' tron stream, and, hence, has all the usual advantages of electronic control. At the same time, these arrangements are not dependent upon a source of heat energy located in close physical proximity to the emitting surface to overcome the work function of the emitter. Therefore, the source of emission energy may be isolated to a high degree from the high voltage current being controlled.

Since many changes could be made in the apparatus shown and described, all within the scope and spirit of the invention, the foregoing is to be construed as illustrative, and not in a limiting What is claimed is:

1. In a circuit for transferring energy between a source of alternating potential and a load terminal, in combination, a network for connecting said load terminal to said source, said network including an electrode adapted to emit electrons upon bombardment with elemental energy particles, a second electrode for collecting electrons emitted by said first electrode, one of said electrodes being operatively connected with said terminal and the other of said electrodes being operatively connected with said source, and a source of elemental energy particles for bombarding said first electrode.

2. A circuit in accordance with claim 1 in which said collecting electrode is physically disposed in sufiicient proximity to said particle source in a manner to create an electrostatic field in the region of said source, and means for establishing a predetermined potential relationship between said collecting electrode and said source.

3. A circuit in accordance with claim 1 in which said collecting electrode is disposed near said particle source, and further including a constant-potential source for maintaining said collecting electrode at a slight positive potential with respect to said particle source.

4. A circuit in accordance with claim 1 including means for returning particles emitted by said particle source to said particle source during the portion of the operating cycle of the network in which said collecting electrode is at a lower potential than said emitting electrode.

5. A circuit in accordance with claim 1v in which said collecting electrode is disposed between said particle source and said emitting electrode and in which the potential on said collecting electrode falls below the potential of said particle source when the potential of said particle source falls below the potential of said emit-v particle source, and means for varying the potential on said control electrode between values above and below the potential of said particle source, sald means being arranged to bias said control electrode negatively with respect to said particle source during portions or the cycle in which said collectin electrode is at a lower potential than said emitting electrode.

7. A circuit in accordance with claim 1 in which said network includes means for limiting the period during which particles will strike said first electrode to less than a full cycle of operation of the network.

8. A circuit in accordance with claim 1 including a third electrode for controlling the flow of particles from said particles source, said third electrode being operated at a potential bearing a predetermined relationship with the potential of said potential source.

9. In a voltage supply circuit including a terminal to which power is to be delivered at a substantially fixed voltage and a source of alternating potential, in combination, a transfer network comprising a first electrode adapted to emit electrons upon bombardment by elemental energy particles, a second electrode adapted to collect electrons emitted by the first electrode, and a source of particles for bombarding said first electrode, one of said electrodes being operatively connected to said terminal and the other of said electrodes being operatively connected to said source, a control electrode interposed between said first electrode and said particle source, and means for varying the potential. of said control electrode in synchronism with the variation of the potential of said potential source so as to prevent the bombardment of said first electrode during periods when said first electrode is at a positive potential with respect to said second electrode.

10. A voltage transfer network comprising a source of alternating voltage, and a capacitor and a transfer circuit serially connected across said source, said transfer circuit including a first circuit element adapted to emit electrons upon bombardment by elemental energy particles, a source of such particles, and a second circuit element for collecting electrons emitted by said first element.

11. An electrical network comprising a source of electrical energy, a first circuit element adapted to emit electrons when bombarded by elemental energy particles, a source of such particles, a second circuit element disposed to collect electrons emitted by said first element, and a capacitor, said capacitor and said circuit elements being serially connected across said source of alternating current.

12. A network in accordance with claim 11 in which said first circuit element comprises a material having a secondary-electron emission ratio greate than one.

13. A network in accordance with claim 11 in which said particle source is a thermionic electron-discharge element.

14. A network in accordance with claim 11 in which said first circuit element comprises a photo-emissive material.

15. A voltage multiplier circuit for use with a two-terminal source of alternating potential, said circuit comprising a plurality of electron discharge devices each comprising a first electrode adapted to emit electrons upon bombardment with elemental energy particles and a second electrode for collecting electrons emitted by said first electrode, a capacito associated with each of said devices, the emitting electrode of one of said devices being connected to a first source terminal through a first capacitor, and the collector of said one device being connected to the second source terminal, and the emitting electrode of a second of said devices being serially connected to the second source terminal through a second capacitor and the collecto electrode of said second device being connected to the emitting electrode of said one device, and a source of elemental energy particles for bombarding said first electrode.

16. A circuit in accordance with claim 15 in which the emitting electrode or" a third one of said devices is connected to the collector electrode of said second device through a capacitor and in which the collecting electrode of said third device is connected to the emitting electrode of said second device.

LAWRENCE J. GIACOLETTO.

No references cited. 

